Academic Commons Search Resultshttp://academiccommons.columbia.edu/catalog.rss?f%5Bauthor_facet%5D%5B%5D=Ting%2C+Mingfang&f%5Bgenre_facet%5D%5B%5D=Articles&q=&rows=500&sort=record_creation_date+desc
Academic Commons Search Resultsen-usInfluence of local and remote SST on North Atlantic tropical cyclone potential intensityhttp://academiccommons.columbia.edu/catalog/ac:187385
Camargo, Suzana J.; Ting, Mingfang; Kushnir, Yochananhttp://dx.doi.org/10.7916/D8988677Thu, 23 Jul 2015 12:39:46 +0000We examine the role of local and remote sea surface temperature (SST) on the tropical cyclone potential intensity in the North Atlantic using a suite of model simulations, while separating the impact of anthropogenic (external) forcing and the internal influence of Atlantic Multidecadal Variability. To enable the separation by SST region of influence we use an ensemble of global atmospheric climate model simulations forced with historical, 1856–2006 full global SSTs, and compare the results to two other simulations with historical SSTs confined to the tropical Atlantic and to the tropical Indian Ocean and Pacific. The effects of anthropogenic plus other external forcing and that of internal variability are separated by using a linear, “signal-to-noise” maximizing EOF analysis and by projecting the three model ensemble outputs onto the respective external forcing and internal variability time series. Consistent with previous results indicating a tampering influence of global tropical warming on the Atlantic hurricane potential intensity, our results show that non-local SST tends to reduce potential intensity associated with locally forced warming through changing the upper level atmospheric temperatures. Our results further indicate that the late twentieth Century increase in North Atlantic potential intensity, may not have been dominated by anthropogenic influence but rather by internal variability.Geophysics, Hydrologic sciences, Climate changesjc71, mt2204, yk16Lamont-Doherty Earth ObservatoryArticlesThe Effect of Topography on Storm-Track Intensity in a Relatively Simple General Circulation Modelhttp://academiccommons.columbia.edu/catalog/ac:166878
Son, Seok-Woo; Polvani, Lorenzo M.; Ting, Mingfanghttp://hdl.handle.net/10022/AC:P:22098Fri, 01 Nov 2013 00:00:00 +0000The effect of topography on storm-track intensity is examined with a set of primitive equation model integrations. This effect is found to be crucially dependent on the latitudinal structure of the background flow impinging on the topography. If the background flow consists of a weak double jet, higher topography leads to an intensification of the storm track downstream of the topography, consistent with enhanced baroclinicity in that region. However, if the background flow consists of a strong single jet, topography weakens the storm track, despite the fact that the baroclinicity downstream of the topography is again enhanced. The different topographic impact results from the different wave packets in the two background flows. For a weak double-jet state, wave packets tend to radiate equatorward and storm-track eddies grow primarily at the expense of local baroclinicity. In contrast, for a strong single-jet state, wave packets persistently propagate in the zonal direction and storm tracks are affected not only by local baroclinicity but also by far-upstream disturbances via downstream development. It is the reduction of the latter by the topography that leads to weaker storm tracks in a strong single-jet state. The implications of these findings for Northern Hemisphere storm tracks are also discussed.Atmospheric sciences, Meteorology, Applied mathematicssws2112, lmp3, mt2204Ocean and Climate Physics, Applied Physics and Applied Mathematics, Lamont-Doherty Earth Observatory, Earth and Environmental SciencesArticlesAtmospheric Circulation Response to an Instantaneous Doubling of Carbon Dioxide. Part II: Atmospheric Transient Adjustment and Its Dynamicshttp://academiccommons.columbia.edu/catalog/ac:159148
Shaw, Tiffany Ann; Seager, Richard; Ting, Mingfang; Naik, Naomi H.; Wu, Yutianhttp://hdl.handle.net/10022/AC:P:19748Fri, 12 Apr 2013 00:00:00 +0000The dynamical mechanisms underlying the transient circulation adjustment in the extratropical atmosphere after the instantaneous doubling of carbon dioxide are investigated using the National Center for Atmospheric Research Community Atmosphere Model version 3 coupled to a Slab Ocean Model. It is shown that the transient process during the first few months of integration is important in setting up the extratropical circulation response in equilibrium such as the poleward shift of the tropospheric jet streams. Three phases are found during the transient thermal/dynamical adjustment in the Northern Hemisphere: 1) a radiatively driven easterly anomaly in the subpolar stratosphere, 2) an acceleration of the westerly anomaly in the subpolar stratosphere as a result of anomalous planetary-scale eddy momentum flux convergence, and 3) a “downward migration” of the westerly anomaly from the lower stratosphere to the troposphere, followed by the tropospheric jet shift. Several proposed mechanisms for inducing the poleward shift of the tropospheric jet streams are examined. No significant increase in eddy phase speed is found. The rise in tropopause height appears to lead the tropospheric jet shift but no close relation is observed. The length scale of transient eddies does increase but does not lead the tropospheric jet shift. Finally, the tropospheric jet shift can be captured by changes in the index of refraction and the resulting anomalous eddy propagation in the troposphere.Atmospheric sciences, Climate changetas2163, rs229, mt2204, nhn2Lamont-Doherty Earth Observatory, Earth and Environmental SciencesArticlesHave Aerosols Caused the Observed Atlantic Multidecadal Variability?http://academiccommons.columbia.edu/catalog/ac:159154
Ting, Mingfang; Delworth, Thomas L.; Zhang, Rong; Kushnir, Yochanan; Sutton, Rowan; Hodson, Daniel L. R.; Dixon, Keith W.; Held, Isaac M.; Marshall, John; Msadek, Rym; Ming, Yi; Robson, Jon; Rosati, Anthonoy J.; Vecchi, Gabriel A.http://hdl.handle.net/10022/AC:P:19750Fri, 12 Apr 2013 00:00:00 +0000Identifying the prime drivers of the twentieth-century multidecadal variability in the Atlantic Ocean is crucial for predicting how the Atlantic will evolve in the coming decades and the resulting broad impacts on weather and precipitation patterns around the globe. Recently, Booth et al. showed that the Hadley Centre Global Environmental Model, version 2, Earth system configuration (HadGEM2-ES) closely reproduces the observed multidecadal variations of area-averaged North Atlantic sea surface temperature in the twentieth century. The multidecadal variations simulated in HadGEM2-ES are primarily driven by aerosol indirect effects that modify net surface shortwave radiation. On the basis of these results, Booth et al. concluded that aerosols are a prime driver of twentieth-century North Atlantic climate variability. However, here it is shown that there are major discrepancies between the HadGEM2-ES simulations and observations in the North Atlantic upper-ocean heat content, in the spatial pattern of multidecadal SST changes within and outside the North Atlantic, and in the subpolar North Atlantic sea surface salinity. These discrepancies may be strongly influenced by, and indeed in large part caused by, aerosol effects. It is also shown that the aerosol effects simulated in HadGEM2-ES cannot account for the observed anticorrelation between detrended multidecadal surface and subsurface temperature variations in the tropical North Atlantic. These discrepancies cast considerable doubt on the claim that aerosol forcing drives the bulk of this multidecadal variability.Atmospheric sciences, Hydrologic sciencesmt2204, yk16Lamont-Doherty Earth Observatory, Earth and Environmental SciencesArticlesMediterranean precipitation climatology, seasonal cycle, and trend as simulated by CMIP5http://academiccommons.columbia.edu/catalog/ac:154117
Kelley, Colin Patrick; Ting, Mingfang; Seager, Richard; Kushnir, Yochananhttp://hdl.handle.net/10022/AC:P:15183Mon, 05 Nov 2012 00:00:00 +0000Winter and summer Mediterranean precipitation climatology and trends since 1950 as simulated by the newest generation of global climate models, the Coupled Model Intercomparison Project phase 5 (CMIP5), are evaluated with respect to observations and the previous generation of models (CMIP3) used in the Intergovernmental Panel on Climate Change Fourth Assessment Report. Observed precipitation in the Mediterranean region is defined by wet winters and drier summers, and is characterized by substantial spatial and temporal variability. The observed drying trend since 1950 was predominantly due to winter drying, with very little contribution from the summer. However, in the CMIP5 multimodel mean, the precipitation trend since 1950 is evenly divided throughout the seasonal cycle. This may indicate that in observation, multidecadal internal variability, particularly that associated with the North Atlantic Oscillation (NAO), dominates the wintertime trend. An estimate of the observed externally forced trend shows that winter drying dominates in observations but the spatial patterns are grossly similar to the multimodel mean trend. The similarity is particularly robust in the eastern Mediterranean region, indicating a radiatively forced component being stronger there. Results of this study also reveal modest improvement for the CMIP5 multi-model ensemble in representation of the observed six month winter and summer climatology. The results of this study are important for assessment of model predictions of hydroclimate change in the Mediterranean region, often referred to as a "hotspot" of future subtropical drying.Climate changecpk2111, mt2204, rs229, yk16Lamont-Doherty Earth Observatory, Earth and Environmental SciencesArticlesStructure and variances of equatorial zonal circulation in a multimodel ensemblehttp://academiccommons.columbia.edu/catalog/ac:153385
Yu, Bin; Zwiers, Francis W.; Boer, George J.; Ting, Mingfanghttp://hdl.handle.net/10022/AC:P:14957Tue, 16 Oct 2012 00:00:00 +0000The structure and variance of the equatorial zonal circulation, as characterized by the atmospheric mass flux in the equatorial zonal plane, is examined and inter-compared in simulations from 9 CMIP3 coupled climate models with multiple ensemble members and the NCEP-NCAR and ERA-40 reanalyses. The climate model simulations analyzed here include twentieth century (20C3M) and twenty-first century (SRES A1B) simulations. We evaluate the 20C3M modeled zonal circulations by comparing them with those in the reanalyses. We then examine the variability of the circulation, its changes with global warming, and the associated thermodynamic maintenance. The tropical zonal circulation involves three major components situated over the Pacific, Indian, and Atlantic oceans. The three cells are supported by the corresponding diabatic heating extending deeply throughout the troposphere, with heating centers apparent in the mid-troposphere. Seasonal features appear in the zonal circulation, including variations in its intensity and longitudinal migration. Most models, and hence the multi-model mean, represent the annual and seasonal features of the circulation and the associated heating reasonably well. The multi-model mean reproduces the observed climatology better than any individual model, as indicated by the spatial pattern correlation and mean square difference of the mass flux and the diabatic heating compared to the reanalysis based values. Projected changes in the zonal circulation under A1B forcing are dominated by mass flux changes over the Pacific and Indian oceans. An eastward shift of the Pacific Walker circulation is clearly evident with global warming, with anomalous rising motion apparent over the equatorial central Pacific and anomalous sinking motions in the west and east, which favors an overall strengthening of the Walker circulation. The zonal circulation weakens and shifts westwards over the Indian Ocean under external forcing, whereas it strengthens and shifts slightly westwards over the Atlantic Ocean. The forced circulation changes are associated with broad SST and atmospheric diabatic heating changes in the tropics. Linear trends of these forced circulation changes, as characterized by regional spatial maximum amplitudes of mass fluxes and their longitudes over the three oceans, are statistically significant at the 5 % level for 2000–2099 for the multi-model mean. However, wide differences of the trends are apparent across the models, because of both deficiencies in the simulation of the circulations in different models and the high internal variability of the circulations.Atmospheric sciences, Climate changemt2204Lamont-Doherty Earth Observatory, Earth and Environmental SciencesArticlesIntensification of Northern Hemisphere subtropical highs in a warming climatehttp://academiccommons.columbia.edu/catalog/ac:153382
Li, Wenhong; Li, Laifang; Ting, Mingfang; Liu, Yiminhttp://hdl.handle.net/10022/AC:P:14956Tue, 16 Oct 2012 00:00:00 +0000Semi-permanent high-pressure systems over the subtropical oceans, known as subtropical highs, influence atmospheric circulation, as well as global climate. For instance, subtropical highs largely determine the location of the world’s subtropical deserts, the zones of Mediterranean climate and the tracks of tropical cyclones. The intensity of two such high-pressure systems, present over the Northern Hemisphere oceans during the summer, has changed in recent years. However, whether such changes are related to climate warming remains unclear. Here, we use climate model simulations from the Intergovernmental Panel on Climate Change Fourth Assessment Report, reanalysis data from the 40-year European Centre for Medium-Range Weather Forecasts, and an idealized general circulation model, to assess future changes in the intensity of summertime subtropical highs over the Northern Hemisphere oceans. The simulations suggest that these summertime highs will intensify in the twenty-first century as a result of an increase in atmospheric greenhouse-gas concentrations. We further show that the intensification of subtropical highs is predominantly caused by an increase in thermal contrast between the land and ocean. We suggest that summertime near-surface subtropical highs could play an increasingly important role in regional climate and hydrological extremes in the future.Meteorology, Climate changemt2204Lamont-Doherty Earth Observatory, Earth and Environmental SciencesArticlesThe relative contributions of radiative forcing and internal climate variability to the late 20th Century winter drying of the Mediterranean regionhttp://academiccommons.columbia.edu/catalog/ac:143914
Kelley, Colin Patrick; Ting, Mingfang; Seager, Richard; Kushnir, Yochananhttp://hdl.handle.net/10022/AC:P:12405Tue, 31 Jan 2012 00:00:00 +0000The roles of anthropogenic climate change and internal climate variability in causing the Mediterranean region's late 20th Century extended winter drying trend are examined using 19 coupled models from the Intergovernmental Panel on Climate Change Fourth Assessment Report. The observed drying was influenced by the robust positive trend in the North Atlantic Oscillation (NAO) from the 1960s to the 1990s. Model simulations and observations are used to assess the probable relative roles of radiative forcing, and internal variability in explaining the circulation trend that drove much of the precipitation change. Using the multi-model ensemble we assess how well the models can produce multidecadal trends of realistic magnitude, and apply signal-to-noise maximizing EOF analysis to obtain a best estimate of the models' (mean) sea-level pressure (SLP) and precipitation responses to changes in radiative forcing. The observed SLP and Mediterranean precipitation fields are regressed onto the timeseries associated with the models' externally forced pattern and the implied linear trends in both fields between 1960 and 1999 are calculated. It is concluded that the radiatively forced trends are a small fraction of the total observed trends. Instead it is argued that the robust trends in the observed NAO and Mediterranean rainfall during this period were largely due to multidecadal internal variability with a small contribution from the external forcing. Differences between the observed and NAO-associated precipitation trends are consistent with those expected as a response to radiative forcing. The radiatively forced trends in circulation and precipitation are expected to strengthen in the current century and this study highlights the importance of their contribution to future precipitation changes in the region.Climate change, Atmospheric sciencescpk2111, mt2204, rs229, yk16Lamont-Doherty Earth Observatory, Earth and Environmental SciencesArticlesRobust features of Atlantic multi-decadal variability and its climate impactshttp://academiccommons.columbia.edu/catalog/ac:143810
Ting, Mingfang; Kushnir, Yochanan; Seager, Richard; Li, Cuihuahttp://hdl.handle.net/10022/AC:P:12333Tue, 24 Jan 2012 00:00:00 +0000Atlantic Multi-decadal Variability (AMV), also known as the Atlantic Multi-decadal Oscillation (AMO), is characterized by a sharp rise and fall of the North Atlantic basin-wide sea surface temperatures (SST) on multi-decadal time scales.Widespread consequences of these rapid temperature swings were noted in many previous studies. Among these are the drying of Sahel in the 1960-70s and change in the frequency and intensity of Atlantic hurricanes on multi-decadal time scales. Given the short instrumental data records (about a century long) the central question is whether these climate fluctuations are robustly linked with the AMV and to what extent are these connections subject to changes in a changing climate. Here we address this issue by using the CMIP3 simulations for the 20th, 21st, and pre-industrial eras with 23 IPCC models. While models tend to produce AMV of shorter time scales and less periodic than suggested by the observations, the spatial structures of the SST anomaly patterns, and their association with worldwide precipitation, are surprisingly similar between models (with differing external forcing) and observations. Our results confirm the strong link between AMV and Sahel rainfall and suggest a clear physical mechanism for the linkage in terms of meridional shifts of the Atlantic ITCZ. The results also help clarify influences that may not be robust, such as the impacts over North America, India, and Australia.Climate changemt2204, yk16, rs229, cl889Lamont-Doherty Earth ObservatoryArticlesChanges in storm tracks and energy transports in a warmer climate simulated by the GFDL CM2.1 modelhttp://academiccommons.columbia.edu/catalog/ac:134168
Wu, Yutian; Ting, Mingfang; Seager, Richard; Huang, Huei-Ping; Cane, Mark A.Mon, 20 Jun 2011 00:00:00 +0000Storm tracks play a major role in regulating the precipitation and hydrological cycle in midlatitudes. The changes in the location and amplitude of the storm tracks in response to global warming will have significant impacts on the poleward transport of heat, momentum and moisture and on the hydrological cycle. Recent studies have indicated a poleward shift of the storm tracks and the midlatitude precipitation zone in the warming world that will lead to subtropical drying and higher latitude moistening. This study agrees with this key feature for not only the annual mean but also different seasons and for the zonal mean as well as horizontal structures based on the analysis of Geophysical Fluid Dynamics Laboratory (GFDL) CM2.1 model simulations. Further analyses show that the meridional sensible and latent heat fluxes associated with the storm tracks shift poleward and intensify in both boreal summer and winter in the late twenty-first century (years 2081-2100) relative to the latter half of the twentieth century (years 1961-2000). The maximum dry Eady growth rate is examined to determine the effect of global warming on the time mean state and associated available potential energy for transient growth. The trend in maximum Eady growth rate is generally consistent with the poleward shift and intensification of the storm tracks in the middle latitudes of both hemispheres in both seasons. However, in the lower troposphere in northern winter, increased meridional eddy transfer within the storm tracks is more associated with increased eddy velocity, stronger correlation between eddy velocity and eddy moist static energy, and longer eddy length scale. The changing characteristics of baroclinic instability are, therefore, needed to explain the storm track response as climate warms. Diagnosis of the latitude-by-latitude energy budget for the current and future climate demonstrates how the coupling between radiative and surface heat fluxes and eddy heat and moisture transport influences the midlatitude storm track response to global warming. Through radiative forcing by increased atmospheric carbon dioxide and water vapor, more energy is gained within the tropics and subtropics, while in the middle and high latitudes energy is reduced through increased outgoing terrestrial radiation in the Northern Hemisphere and increased ocean heat uptake in the Southern Hemisphere. This enhanced energy imbalance in the future climate requires larger atmospheric energy transports in the midlatitudes which are partially accomplished by intensified storm tracks. Finally a sequence of cause and effect for the storm track response in the warming world is proposed that combines energy budget constraints with baroclinic instability theory.Environmental scienceyw2225, mt2204, rs229, mac6Applied Physics and Applied Mathematics, Lamont-Doherty Earth Observatory, Earth and Environmental SciencesArticlesAtmospheric Circulation Response to an Instantaneous Doubling of Carbon Dioxide Part I: Model Experiments and Transient Thermal Response in the Tropospherehttp://academiccommons.columbia.edu/catalog/ac:134171
Wu, Yutian; Seager, Richard; Ting, Mingfang; Naik, Naomi H.; Shaw, Tiffany Annhttp://hdl.handle.net/10022/AC:P:10556Mon, 20 Jun 2011 00:00:00 +0000This study aims to understand the dynamical mechanisms driving the changes in the general circulation of the atmosphere due to increased carbon dioxide (CO2) by looking into the transient step-by-step adjustment of the circulation. The transient atmospheric adjustment is examined using the National Center for Atmospheric Research Community Atmospheric Model Version 3 coupled to a slab ocean model and the CO2 concentration in the atmosphere is uniformly and instantaneously doubled. The thermal structure and circulation response is well established after one year of integration with the magnitudes gradually increasing afterwards towards quasi-equilibrium. Tropical upper tropospheric warming occurs in the first month. The expansion of the warming in the middle and upper troposphere to the subtropics occurs later and is found to be primarily dynamically-driven due to the intensification of transient eddy momentum flux convergence and resulting anomalous descending motion in this region. The poleward displacement of the midlatitude tropospheric jet streams occurs together with the change in eddy momentum flux convergence but only after the intensification of the subpolar westerlies in the stratosphere. The results demonstrate the importance of the tropospheric eddies in setting up the extratropical tropospheric response to global warming.Environmental scienceyw2225, rs229, mt2204, nhn2, tas2163Applied Physics and Applied Mathematics, Lamont-Doherty Earth Observatory, Earth and Environmental SciencesArticlesNorthern Hemisphere winter snow anomalies: ENSO, NAO and the winter of 2009/10http://academiccommons.columbia.edu/catalog/ac:134161
Seager, Richard; Kushnir, Yochanan; Nakamura, Jennifer A.; Ting, Mingfang; Naik, Naomi H.http://hdl.handle.net/10022/AC:P:10553Mon, 20 Jun 2011 00:00:00 +0000Winter 2009/10 had anomalously large snowfall in the central parts of the United States and in northwestern Europe. Connections between seasonal snow anomalies and the large scale atmospheric circulation are explored. An El NiÃ±o state is associated with positive snowfall anomalies in the southern and central United States and along the eastern seaboard and negative anomalies to the north. A negative NAO causes positive snow anomalies across eastern North America and in northern Europe. It is argued that increased snowfall in the southern U.S. is contributed to by a southward displaced storm track but further north, in the eastern U.S. and northern Europe, positive snow anomalies arise from the cold temperature anomalies of a negative NAO. These relations are used with observed values of NINO3 and the NAO to conclude that the negative NAO and El NiÃ±o event were responsible for the northern hemisphere snow anomalies of winter 2009/10.Environmental sciencers229, yk16, jam148, mt2204, nhn2Lamont-Doherty Earth Observatory, Earth and Environmental SciencesArticlesMechanisms of Tropical Atlantic SST Influence on North American Precipitation Variabilityhttp://academiccommons.columbia.edu/catalog/ac:134152
Kushnir, Yochanan; Seager, Richard; Ting, Mingfang; Naik, Naomi H.; Nakamura, Jennifer A.http://hdl.handle.net/10022/AC:P:10551Mon, 20 Jun 2011 00:00:00 +0000The dynamical mechanisms associated with the impact of year-to-year variability in tropical North Atlantic (TNA) sea surface temperatures (SSTs) on North American precipitation, during the cold and warm halves of the hydrological year (October–September) are examined. Observations indicate that during both seasons warmer-than-normal TNA SSTs are associated with a reduction of precipitation over North America, mainly west of 90°W, and that the effect can be up to 30% of the year-to-year seasonal precipitation RMS variability. This finding confirms earlier studies with observations and models. During the cold season (October–March) the North American precipitation variability associated with TNA fluctuations is considerably weaker than its association with ENSO. During the warm season (April–September), however, the Atlantic influence, per one standard deviation of SST anomalies, is larger than that of ENSO. The observed association between TNA SST anomalies and global and North American precipitation and sea level pressure variability is compared with that found in the output of an atmospheric general circulation model (AGCM) forced with observed SST variability, both globally and in the tropical Atlantic alone. The similarity between model output and observations suggests that TNA SST variability is causal. The mechanisms of the “upstream” influence of the Atlantic on North American precipitation are seasonally dependent. In the warm season, warmer-than-normal TNA SSTs induce a local increase in atmospheric convection. This leads to a weakening of the North Atlantic subtropical anticyclone and a reduction in precipitation over the United States and northern Mexico, associated with the anomalous southward flow there. In the cold season, a response similar to the warm season over the subtropical Atlantic is identified, but there is also a concomitant suppression of convection over the equatorial Pacific, which leads to a weakening of the Aleutian low and subsidence over western North America, similar to the impact of La Niña although weaker in amplitude. The impact of TNA SST on tropical convection and the extratropical circulation is examined by a set of idealized experiments with a linear general circulation model forced with the tropical heating field derived from the full AGCM.Environmental scienceyk16, rs229, mt2204, nhn2, jam148Lamont-Doherty Earth Observatory, Earth and Environmental SciencesArticlesThe role of linear wave refraction in the transient eddy-mean flow response to tropical Pacific SST anomalieshttp://academiccommons.columbia.edu/catalog/ac:134149
Harnik, Nili; Seager, Richard; Naik, Naomi H.; Cane, Mark A.; Ting, Mingfanghttp://hdl.handle.net/10022/AC:P:10550Mon, 20 Jun 2011 00:00:00 +0000The midlatitude response to tropical Pacific SST anomalies involves changes in transient eddy propagation, but the processes leading to the transient eddy changes are still not clear. In a recent study, we used a series of controlled general circulation model (GCM) experiments in which an imposed tropical Pacific sea-surface temperature (SST) anomaly is turned on abruptly and the response is analyzed in terms of its high- and low-frequency parts, to show that the changes in transient eddies induced by El Niño Southern Oscillation (ENSO) arise from changes in wave refraction on the altered mean flow. In this work, we use a quasi-geostrophic linear model and a linear stationary wave model, to interpret the GCM experiments and obtain the sequence of events that lead from a tropical SST anomaly to the quasi-equilibrium change in the mean and transient atmospheric circulation. The initial direct response of the mean flow is confined to the tropical and subtropical Pacific, similar to what is obtained from a stationary wave model. This tropical–subtropical mean flow change initiates a transient eddy response, which induces a midlatitude mean flow anomaly. The wave–mean flow system evolves towards a state in which the eddy anomalies maintain the mean flow anomalies, allowing them to persist. It is further shown that, while eddy momentum fluxes persistently accelerate and decelerate the subtropical and midlatitude mean flow, the eddy heat flux effect on the zonal mean flow is much more variable, and only marginally significant. The linear quasi-geostrophic model calculations capture the evolution of eddy momentum flux anomalies equatorwards of 60°N quite well, suggesting linear wave refraction can explain the midlatitude ENSO anomalies. However, other processes, like stationary waves or changes in the nonlinear stage of eddy life cycles, are needed to explain the ENSO-related anomalies at high latitudes, polewards of around 60°N.Environmental sciencenh2019, rs229, nhn2, mac6, mt2204Applied Physics and Applied Mathematics, Lamont-Doherty Earth Observatory, Earth and Environmental SciencesArticles